Vapor generation



Search Room I h I-IYUIL! llLfta U10 CROSS REFERENCE 4?; VAFORFZ S,

G. w. KESSLE R VAPOR GENERATION 3 5 Oct. so, 1945.

Filed July 15, 1942 2 Sheets-Sheet 1 IIIIIIIIIIII/I/I zzvmvroaGeorge'Wifessler A TI'ORNE Y UHUSS REFERENUI: bfifii'C'ii h0g3? z;var-{Trim Oct. 30, 1945. e. w. KESSLER VAPOR GENERATION Filed July 15,1942 2 Sheets-Sheet 2 I N V EN TOR. George W/ ess/er -A ITORNE YPatented Oct. 30, 1945 VAPOR GENERATION George W. Kessler, New York, N.Y., asslgnor to The Babeoclr 8r Wilcox Company, Jersey City, N. .L, acorporation of New Jersey Application my 15, 1942, Serial No. 450,964

6 Glaims.

The present invention relates in general to the construction andoperation of tubular vapor generating. units incorporating a pluralityof.independently fired furnaces and. a'vapor superheati'ng devicearranged for effective control oi vapor superheat temperatures over arelatively wide load range, and more particularly, to the constructionand operation of water tube steam. boilers of the character describedfor use in the marine field.

The main object of my invention is the provision of a steam generating.unit of the character described. having a plurality of independentlycontrollable furnaces connected to a common heating gas outlet andparticularly characterized by an improved construction and airrangementof the steam generating and superheating, surface of the unit relativeto the furnaces and gas outlet which aflord an effective controI ofsuperheat temperatures over a wide load range, adequate protection ofthe steam superheater at starting-up and. low Ioad periods, heating gastemperatures at the. superheater permitting the use of carbon steelorthe lower grades of heat resisting alloy steel for the superheatertubes, a substantial reduction inthe size of superheater, a low pressuredlfierential between the furnace chambers, a high overall thermalethciency, and a reduction in size, weight and. cost for a givencapacity unit.

The various features of. novelty which characterize my invention arepointed outwith particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should. be had. to the accompanying drawings and descriptivematter in which I have fuel burners. are located. The pressure parts ofthe unit include an upper horizontally arranged steam and. water drum20, a laterally offset lower water drum 2t connectedto the drum 20 by aninclined, bank. of steam generating. tubes 22, and a second lower waterdrum or header 23 horizontally arranged below the drum. 20 and connectedthereto by a substantially vertical. bank of steam generating. tubes 24;A row of water tubes 25 extends downwardly from the drum 20 along theroof section [B and side wall. I to a horizontally arranged wall header25 at approximately the level of the. drum 23.

The described spaced groups of steam generating tubes, in coniunctionwith the front and rear inner walls, define a main furnace chamberbetween the. tube banks 22' and 24, and an auxiliary furnace chamber 3|between the tube groups. 26 and 25. The fornace chambers 31! and 3| areindependently fired by separate groups oi liquid fuel bumers 33 and 3Erespectively arranged, to discharge horizontally through corresponding,burner ports formed. in the front wall l0. As shown, the four burners 33are arranged in the lower part of the furnace wall "I, three being inarow parallel to the inclination of the tube bank 22,, while the fourfuel burners 34 are arranged in. supe p sed relation in. a row parallelto the tube bank 24 and illustrated and described a preferred embodimentof my invention 0f the drawings:

Fig. I is a sectional elevationoi a marine steam generating unitembodying my invention; and. FlFigI. 2 is a section taken on the line2-2. of

The steam generating unit illustrated has a setting of substantiallyhorizontal rectangular cross-section formed. by a double-walled casingincluding inner and outer front walls [0 and H respectivehp inner andouter rear walls [2 and 13 respectively, and inner and outer side wallsM and I 5 respectively with upper inclined roof portions. l6 and l T.respectively. The opposite side of the unit is defined by inner andouterwalls 58 and [9 respectively. The spaced walls of the setting serveas flow passages for combustion air entering one or more air-inlets 2'!in the rear portion of the setting, the air flow cool-- ing the wallsandbeing preheated during its passage to the double front of the unitwhere the the. lower part of the tubes 25. In all cases the burners. arespaced a-suihcient distance from the steam generating tubes to prevent.flame impingement thereon and permit stable ignition and combustionconditions regardless of the number of fuel burners in operation. Thenumber of fuel burners provided and their relative location is dependentupon the load and total steam temperature requirements. The upperportion of the setting at the. outer side of the tube bank 22 isprovided with a. beating gas outlet 411 through which flow all of theheating gases generated in the unit. Auxiliary heating surface, such asan economizer or air heater 41, is positioned in the gas outlet M1 atapproximately the level oi the drum 2!]. The described arrangement ofthe furnaces, steam generating parts and heating gas outlet isparticularly adapted; for marine service in view of the adaptability orsuch units for arrangement in pairs and the permissible compactarrangement of the deck openings for the stack connections (not shown).

The steam generating surface is constructed and arranged to provide amaximum thermal efliciency and a low draft loss tor the unit In oneembodiment of the invention having a total evaporation at full powerrating of approximating 122,500 pounds of steam per hr, the outboard rowof tubes 25 is formed. by 2" 0.. D. studded tubes on 3 /1." centerscovered refractory material 3. The vertical tube bank 24 is formed bytwo outer staggered rows of tubes on each side of 2" O. D. on 3%,"centers and six inner staggered rows of 1" 0. D. tubes on 1 /2" centers.Thetube bank 22 isformed by four staggered rows of 2" O. D. tubes on 4%"centers along its furnace side and fifteen staggered rows of l" O. D.tubes on 1 /2" centers outwardly spaced therefrom. The upper ends of thegenerating tubes 22, 24 and 25 are bent t enter the bottom of the drum20 radially and are distributed over substantially the entire exposedsurface of the drum, insuring proper ligament strength and adequateprotection of the exposed section of the drum. The exposed portions ofthe drums 2| and 23 are similarly protected. The circulationrequirements of the unit are supplied by downcomer tubes from the drum20 psitioned in the air spaces between the front and rear double walls,the downcomers 44 serving the side wall header 26, downcomers 45 servingthe drum 23, and downcomers 46 serving the drum 2|. The wall tubes 25can be extended to the drum 23, if desired, eliminating the necessityfor the header 26 and downcomers 44.

The bottom of each of the furnace chambers 30 and 3| is closed by atrough-shaped refractory floor 58, the inclined sides of which areextended upwardly to the corresponding drums and header. Additionalexposed refractory surface for the furnace 30 is provided by a shortvertical partition wall or baflle 59 extending from the drum 23 toapproximately the center line of the uppermost burner 33. The baflle isformed by studding the corresponding portion of the adjacent tube row 24and applying initially plastic refractory to the studded tube portions.The baflie 59 serves in operation to deflect heating gases from thefurnace chamber 3| away from the main ignition and combustion section ofthe furnace chamber 30, while its restricted height provides asubstantial amount of gas flow area across the tube bank 24 for thegases from the furnace 3|, lessening the gas pressure differentialacross the tube bank 24.

In some steam generating units of the general character described thesteam superheating has been accomplished by superheating surfacepositioned within the tube bank 24 in the space occupied by the smalldiameter tubes. A substantial amount of superheating surface will berequired in such a location, since only the heating gases from theauxiliary furnace chamber traverse the superheater, i. e. only a portionof the total heating gases generated in the unit. In such installationsit is usually necessary to use high grade heat resistant alloy steeltubes to insure protection from the high temperatures to which thesuperheater tubes are liable to be exposed in this location. Such asuperheater location is also objectionable in installations where theauxiliary or superheater furnace is liable to be operated intermittentlyand allow condensate to an undesirable extent in the superheater tubes.

In accordance with my invention, the steam superheating requirements ofthe unit are entirely supplied by a convection type superheater locatedin the space defined between the large diameter or water screen tubesand the remaining portion of the tube bank 22. The superheater is formedby a multiplicity of single looped horizontally extending nested tubes5| having their ends connected to inclined headers 52 and 53 arrangedparallel to the tube bank 22 and positioned between the double walls atone end of the unit. As shown, the headers are located be.-

tween the rear walls I2 and I3 and the corresponding section of thefront walls I0 and H is made removable to facilitate replacement of thesuperheater tubes. The superheater tubes are all supported by plates 54carried by some of a group of large diameter inclined support tubes 55positioned within the superheater tube loops and connecting the drums 20and 2|. The superheater headers are divided by transverse diaphragms toprovide a three-pass flow path for the saturated steam entering theupper part of the header 52 and discharging from the lower part of theheader 53 to its point of use. The number of passes for the steam in thesuperheater and the specific arrangement of the same with respect to gasflow is dependent upon the load and total steam temperaturerequirements. In addition to the main steam outlet 56 on drum 20, anadditional outlet 51 is provided for the separate withdrawal ofsaturated steam directly from the drum.

With the described construction and arrangement of the parts the unitcan be started up by the operation of one or more fuel burners in eitherthe main furnace 30 or auxiliary furnace 3|. It is preferable however touse one or more of the auxiliary furnace burners 34 for startingup, dueto the additional protection to the superheater afforded by the tubebank 24 in the flow path of the heating gases from the auxiliaryfurnace. When the main furnace burners are used for starting-up, morecare must be exercised in bringing the unit up to steaming pressure andtemperature. The presence of the rows of tubes 22 at the furnace side ofthe superheater adequately reduces the temperature of the heating gasesbefore contacting with the superheating tubes, when the burners 33 areused at startingup. As the amount of steam flowing through thesuperheater increases, the burners 33 in the main furnace are put intoservice, as well as additional burners 34 in the auxiliary furnace. Dueto the positioning of a substantial amount of convection heated heatabsorbing surface between the furnace chambers, the heating gases fromthe auxiliary furnace 3| are reduced in temperature before entering thefurnace chamber 30 and contacting with the generating tubes 22 andsuperheating tubes 5|.

The superheater is thus screened from the furnace chamber 30 by fourrows of tubes 22 and from the furnace chamber 3| by the entire tube bank24 in addition. By varying the operation of the fuel burners 33 and 34the effectiveness of convection heat absorbing surface in the path ofthe gases contacting with the superheater, and correspondingly thetemperature of those gases, can be varied over a wide range. Usuallyduring normal operation a major portion of the fuel will be burned inthe main furnace chamber 30 and the furnace chamber 3| operated tosupplement the steam generating capacity of the boiler or to providelower temperature heating gases for regulating superheat temperatures.With the dc? scribed capacity for variablefiring of the furnaces andvariable heat absorption of the convection heated surface in the path ofthe heating gases contacting the superheater, a constant superheattemperature can b maintained over the normal range of operating loads.

For limited ratings one or more burners 34 of the auxiliary furnace canbe fired and all of the steam generated by the unit removed directlyfrom the drum 20 through the auxiliary saturated steam outlet 51. Withonly burners 34 in operasamos ation and all of the steam passed throughthe superheater, substantially saturated steam can be obtained at lowratings. At higher ratings, due to the relatively large amount of heatabsorbing surface between the auxiliary furnace and the superheater,very low superheat temperatures can be obtained.

The described relative arrangement of heat absorbing surface andfurnaces is also advantageous in permitting a reduction in the amount ofthe superheating surface required, since all of the heating gasesgenerated in either furnace provide convection heating of thesuperheater tubes. i. e. approximately 2 to 2 times the amount ofheating gases usually contacting with a superheater located within thetube bank 2|. The lower. gas temperatures at the superheater result in alower tube wall temperature and the permissible use of carbon steel orlow grade steel alloy for these tubes. The number of steam passesthrough the superheater is likewise reduced, thus reducing the pressuredrop through the superheater.

The formation of the tube bank between the two furnaces entirely ofclosely spaced vertical water tubes increases the thermal efficiency,minimizes space requirements for a given steam generating capacity, andaffords improved protection for the associated drums; The absence ofsuperheater headers in this location permits a better arrangement ofdowncomer tubes and reduces the number of downcomers which extendcircumferentially around the steam drum.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the'apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

1. A vapor generating and superheatin unit comprising a setting, anupper vapor and liquid drum, a bank of inclined vapor generating tubeshaving their upper ends connected to said drum, a second tube bank ofsubstantial depth and open throughout a major portion of the tube heightand consisting solely of rows of vertically extending vapor generatingtubes arranged to be heated mainly by convection and having their upperends connected to said drum, a furnace chamber arranged between andhaving opposite sides defined by said tube banks, a second furnacechamber at the opposite side of said second tube bank, said secondtubebank defining the gas outlet side of said second furnace chamber,means for independently and variably firing each of said furnacechambers, the vapor superheating surface of said unit consisting solelyof a vapor superheater screened from said first furnace chamher by aplurality of rows of tubes of said first tube bank, the number of tuberows and heat absorbing capacity of said second tube bank beingsubstantially greater than the number and heat absorbing capacity of thetube rows of said first tube bank screening said superheater from saidfirst furnace chamber, a single heating gas outlet for said setting atthe opposite side of said first tube bank from said first furnace.chamber, and said furnace chambers, tube banks, superheater and gasoutlet being so relatively arranged that substantially all of theheating gases from both of said furnace chambers fiow across saidsuperheater and the heating gases from said second furnace chamber flowacross a major portion of the height of the tubes in said second tubebank and through said first furnace chamber prior to flowing across saidfirst tube bank and superheater.

2. A vapor generating and superheatlng unit comprising a setting, anupper vapor and liquid drum, a main bank of inclined vapor generatingtubes having their upper ends connected to said drum, a second tube bankof substantial depth and open throughout a major portion of the tubeheight and consisting solely of rows of vertically extending vaporgenerating tubes arranged to be heated mainly by convection and havingtheir upper ends extending to and directly connected to the lowerportion of said drum over a substantial circumferential area of saiddrum, a'furnace chamber arranged sublacent to said drum and between andhaving opposite sides defined by said tube banks, a second furnacechamber at the opposite side of said second tube bank, said second tubebank defining the gas outlet side of said second furnace chamber, meansfor independently and variably firin each of said furnace chambers, thevapor superheating surface of said unit consisting solely of a vaporsuperheater screened from said first furnace chamber by a plurality ofrows of tubes of said first tube bank, said second tube bank having aheat absorbing capacity at least thirty per cent of the heat absorbingcapacity of said first tube bank and substantially greater in number oftube rows and heat absorbing capacity than the number and heat absorbingcapacity of the tube rows of said first tube bank screening saidsuperheater from said first furnace chamber, a single heating gas outletfor said setting at the opposite Side of said 4.0 first tube bank fromsaid first furnace chamber,

and said furnace chambers, tube banks, superheater and gas outlet beingso relatively arranged that substantially all of the heating gases fromboth of said furnace chambers flow across said superheater and theheating gases from said second furnace chamber flow across a majorportion of the height of the tubes in said second tube bank and throughsaid first furnace chamber prior to flowing across said first tube bankand superheater.

3. A vapor generating and superheating unit comprising a setting. anupper vapor and liquid drum, a bank of inclined vapor generatin tubeshaving their upper ends connected to said drum, a second tube bank ofsubstantial depth and open throughout a major portion of the tube heightand consisting solely ofrows of vertically extending vapor generatingtubes arranged to be heated mainly by convection and having their upperends extending to and so directly connected to said drum as to occupysubstantially the entire drum circumferential area between said firsttube bank and said setting. a furnace chamber arranged subiacent to saiddrum and between and having opposite sides defined by said tube banks, asecond furnace chamber at the opposite side of said second tube bank,said second tube bank definin the gas outlet side of said second furnacechamber, means forming a baille extending along the lower portion ofsaid second tube bank at the first furnace chamber side thereof, burnermeans in an end wall of said setting for independently and variablyfiring each of said furnace chambers, the vapor superheating surface ofsaid unit consisting solely of a nace chamber by a. plurality of rows oftubes of said first tube bank, the number of tube rows and heatabsorbing capacity of said second tube bank being substantially greaterthan the number and: heat absorbing capacity of the tube rows of saidfirst tube bank screening said superheater from said first furnacechamber, a single heating gas outlet for said setting at the oppositeside of said first tube bank from said first furnace chamber, and saidfurnace chambers, tube banks, superheater and gas outlet being sorelatively arranged that substantially all of the I heating gases fromboth of said furnace chambers flow across said superheater and theheating gases from said second furnace chamber fiow across a majorportion of the height of the tubes in said second tube bank, over saidbafile and through the upper part of said first furnace chamber prior'tofiowing across said first tube bank and superheater.

4. A steam generating unit comprising a setting, an upper steam andwater drum, a lower laterally offset water drum, a main bank ofvertically inclined steam generating tubes having their ends connectedto said drums, a second lower drum below said upper drum, a, second tubebank of substantial depth and open throughout a major portion of thetube height and consisting solely of rows of vertically'arranged steamgenerating tubes arranged to be heated mainly by convection and havingtheir ends extendin to and directly connected to the lower portion ofsaid-upper drum and second water drum, means for bottom supporting saidtube banks and drums, a furnace chamber arranged subjacent to said upperdrum and between and having opposite sides defined by said tube banks, asecond furnace chamber at the opposite side of said second tube bank,said second tube bank occupying the gas outlet side of said secondfurnace chamber, means for independently and variably firing each ofsaid furnace chambers, the steam superheating surface of said unitconsisting solely of a. steam superheater screened from said firstfurnace chamber by a plurality of rows of tubes of said first tube bank,the number of tube rows and heat absorbing capacity of said second tubebank being substantially greater than the number and heat absorbingcapacity of the tube rows of said first tube bank screening saidsuperheater from said first furnace chamber, a single heatin gas outletfor said setting at the opposite side of said first tube bank from saidfirst furnace chamber, and said furnace chambers, tube banks,superheater and gas outlet being so relatively arranged thatsubstantially all of the heating gases from both of said furnacechambers flow across said superheater and the heating gases from saidsecond furnace chamber flow across a major portion of the height of thetubes in said second tube bank and through said first furnace chamberprior to flowing across said first tube bank and superheater to said gasoutlet.

'5. A steam generating unit comprising a setting, an upper steam andwater drum, a lateral- 1y offset lower water drum, a bank of verticallyinclined steam generating tubes having their ends connected to saiddrums, a second lower water drum directly below said upper drum, asecond tube bank of substantial depth and open throughout a majorportion of the tube height and convapor superheater screened from saidfirst fursisting solely of rows of vertically arranged steam generatingtubes arranged to be heated mainly-by convection and having their endsextending to and directly connected to the lower portion of said upperdrum and second water drum for a substantial circumferential sector ofsaid drums, means for bottom supportin said tube banks and drums, afurnace chamber arranged subjacent to said upper drum and between andhaving opposite sides defined by said tube banks, a second furnacechamber at the opposite side of said second tube bank, said second tubebank occupying the gas outlet side of said second furnace chamber, meansfor independently and variably firing each of said furnace chamberscomprising a group of fuel burners in an end wall of said settingarranged to discharge into the lower part of said first furnace chamberand a group of superposed fuel burners in an end wall of said settingsubstantially symmetrically arranged relative to said second furnacechamber, the steam superheating surface of said unit consistin solely ofa steam superheater screened from said first furnace chamber by aplurality of rows of tubes of said first tube bank, said second tubebank having a heat absorbing capacity at least thirty per cent of theheat absorbing capacity of said first tube bank and substantiallygreater in number of tube rows and heat absorbing capacity than thenumber and heat absorbing capacity of the tube rows of said first tubebank screening said superheater from said first furnace chamber, asingle heating gas outlet for" said setting at the opposite side of saidfirst tube bank from said first furnace chamber, and said furnacechamber, tube banks, superheater and gas outlet being 50 relativelyarranged that substantially all of the heating gases from both of saidfurnace chambers fiow across said superheater and the heating gases fromsaid second furnace chamber flow across a major portion of the height ofthe tubes in said second tube bank and through said first furnacechamber prior to flowing across said first tube bank and superheater.

6. The method of generating and superheating steam which comprisesburning fuel in a furnace chamber to generate high temperature heatinggases, simultaneously burning fuel in a second furnace chamber togenerate high temperature heating gases, directing the heating gasesfrom said second furnace chamber over a substantial amount of steamgenerating surface receiving heat mainly by convection heating andabsorbing sufficient heat to reduce the temperature of the heating gasesfrom said second furnacechamber substantially below' the temperature ofthe heatin gases generated in said first furnace chamber, directing thelower temperature heating gases from said second furnace chamber throughsaid first furnace chamber in mixing relation with the heating gasesgenerated therein, passing all of the steam to be superheated solelyover steam superheating surface receiving heat mainly by convectionheating, directing substantially all of the mixed heating gase inconvection heat transfer relation with said superheating surface, andvarying the fuel burning rates in one or both of said furnace chambersto vary the temperature of the mixed heating gases directed to saidsuperheating surface and thereby the final superheat temperature.

GEORGE W. KESSLER.

